"This report describes a study that analyzed the relationships between reductions in pollutants from power plants and fine particulate matter (PM2.5) concentrations in the eastern United States between 1999 and 2005. Dr. Richard D. Morgenstern of Resources for the Future and colleagues used a novel data-driven source-receptor model to explore the statistical relationships between source emissions of sulfur dioxide (SO2) and nitrogen oxides and monitored concentrations of PM2.5. They performed various external comparisons of their models, and compared the reductions to an estimated counterfactual scenario in which no mandated reductions in SO2 occurred."--Publisher's website.